Astronomy Chapter 7 - 7.3

On Earth, we can get the age of various parts of our planet by finding rocks that contain radioactive atoms. Which other world do have a good number of rocks from to do this kind of age analysis?

The Moon

Radioactive dating techniques have revealed that our Earth and Moon are approximately how old?

about 4.5 billion years

What is one way that astronomers have actually gotten an idea of the age of the surfaces of terrestrial planets other than the Earth?

counting craters

In radioactive dating, the measure scientists use to note how long (on average) a particular radioactive nucleus will take to decay is called its

half-life

In studying the surfaces of solid bodies in the solar system, astronomers have learned that the number of craters (per unit area):

is roughly proportional to the age of the surface we are examining

In a bad late-night science fiction film, a villain is using a large collection of rare radioactive atoms as energy for a weapon to threaten the good guys. The atoms have a half-life of 1 hour. The villain has 4 kilograms of the radioactive material now, and he needs a minimum of 1 kg. for his weapon to work. After how much time will the weapon no longer be a threat?

just a little after 2 hrs

The rate at which a collection of the same radioactive atoms will decay depends on:

only on internal processes within the atoms; nothing external matters